Terrorists don’t have to travel to a remote training camp – or even to the neighborhood library – to learn how to make a bomb. Step-by-step instructions are easily available online.

The simple pressure cooker bomb apparently used to maim and kill people at the Boston Marathon on Monday is cheap and easy to construct. An article in al Qaida’s online magazine, Inspire, explained how to “make a bomb in the kitchen of your mom” in 2010. More recently, in March, another online publication, The Lone Mujahid Pocketbook, advertised “easy and safe terrorism” and “kitchen fun” on its cover. Inside was a simple three-ingredient recipe for the explosive acetone peroxide. “Should be made in small amounts due to its sensitivity,” the author cautioned.

On YouTube, hundreds of videos demonstrate explosions and instruct viewers in bomb making. One such video, titled “how to make a pipe bomb,” had 7,790 views as of Wednesday. “Holy (expletive) i can actually use this to kill someone,” one commenter wrote admiringly, before signing off with a smiley face emoticon.

“Once upon a time this kind of information was known only to large terrorist groups and maybe to operatives of intelligence organizations of three or four countries. Now it’s available to a 12-year-old,” said Rabbi Abraham Cooper, head of the Digital Terrorism and Hate Project at the Simon Wiesenthal Center, a Jewish human rights organization.

Bomb-making videos and instruction manuals are protected by the Constitution’s First Amendment, which guarantees free speech. Federal law also protects media platforms from liability for the actions of their users.

Cooper wants to see Internet search engines and social media companies take more proactive steps to police the content that users post on these sites.

“To us it’s not about free speech, it’s about thwarting tragedy,” he said.

Cooper’s center has given letter grades to three big social media companies for how well each filters hate speech and “how-to” information about manufacturing bombs or poisons.

Facebook gets an A- because the company removes an immense amount of material and has put safeguards in place to try and locate it faster.

YouTube gets a C-/D+ for removing some offensive material but very little, and “they need to be more proactive,” Cooper said.

Twitter gets an F. Cooper said the company doesn’t have a clearly articulated policy and appears to have removed only a handful of feeds.

“Governments are doing what they can, but they cannot get ahead of the curve on this unless the Internet community steps up to the plate,” he said.

But the sheer volume of material uploaded to the Internet every day makes filtering out dangerous content in real time a Sisyphean task.

Seventy-two hours of material is uploaded to YouTube every minute, for example. The company explicitly prohibits instructional bomb-making videos in its community guidelines, and will remove such content, but only if it’s flagged by viewers.

“We encourage people to flag any material that they believe violates those guidelines,” a YouTube spokeswoman said in a statement. “We’re reviewing these flags around the clock every day, routinely removing anything that breaks the rules.”

Even if Internet and social media sites could somehow delete every bomb-making manual online, determined extremists could still get their hands on printed materials that provide the same information, often in more detail.

The book Timothy McVeigh reportedly used to make the bomb that destroyed the federal building in Oklahoma City – “Homemade C-4: A Recipe for Survival” – is available for purchase on Amazon or in bookstores, as is “The Anarchist Cookbook,” a book that provides homemade recipes for everything from TNT to Molotov cocktails. It was originally published in 1971.

“That information just exists and I think that by trying to criminalize the publication of that information, you’re really going at it from the wrong end,” said Cindy Cohn, legal director of the Electronic Frontier Foundation, a digital civil liberties group. “It’s wrong because it’s inconsistent with our values as a free society and it’s wrong because it will not work.”

If you want to go after crime, you go after the commission of the crime, not information that might be misused, Cohn said.

“I don’t think anybody seriously thinks that the only thing that protects us from terrorists is that terrorists don’t know how to make bombs,” she said.